Grinding



Jan. 9, 1945. A. N. EMMONS v 2,367,107

GRINDING Filed Jan. 12,- 1945 4 Sheets-Sheet l Jan. 9, 1-945. A. N. EMMO'NS 2,367,107

' GRINDING Filed Jan. 12, 1945 4 Sheets-Sheet 2 INVENTOR.

HTTUFNEYS.

Jan. 9, 1945. EMMQNS 2,367,107

' I GRINDING Filed Jan. 12, 1945 4 Sheets-Sheet 5 BY. 4 I

177' IZMNE Y5.

' I I INVENTOR.

Patented-Jan. 9, 1945 Application January 12, 1943, Serial No. 472,095

. Claiins.

This invention has to do in general with grinding, and more particularly with a method of. precision grinding employing apparatus of the belt .type wherein an endless abrasive belt is operated over a pair of pulleys.

Grinding operations have heretofore been carried out by holding the work against an abrasive belt. If the belt were not backed up by a platen,

I the operation was more of a bui'fing or polishing operation to produce a smooth surface to en hance the appearance of the object being operated upon. The prior method also included such an operation with the belt backed by a platen and in that instance, the operation was performed to produce an approximate flat surface. With this method, the surface operated upon was only approximately flat or uniform due to the fact that even though the surface of the platen over which the belt was run was fiat with close limits.

the abrasive belt has a tendency to move relative to the platen, or portions of the belt do not follow the contour of the platen due to curling, uneven tension through the width of the belt, etc. Accordingly, this method. of grinding was only employed for quickly surfacing parts that did not have to be flat within accurate or close limits.

This invention has as an object a method of grinding with an abrasive belt whereby the parts operated upon are finished with a flat surface equivalent to the accuracy of the platen, and the invention further includes a form of apparatus by which the method can be carried out.

The inventionconsists in the novel features an d in the combinations and constructions hereinafter set forth'andclaimed.

In describing this invention, reference is had to the accompanying drawings in which like characters designate corresponding parts in all the views.

Figure 1 is a side elevational view of the machine embodying my invention.

Figure 2 is a view', similar to Figure 1, showing the opposite side of the machine.

Figure 3 is a front'elevational view of the upper portion of the'machine with parts broken away, and parts shown in section.

Figure 4 is a front elevational view of the lower portion of the machine with parts broken away and parts shown in section.

The method consists in holding the work againstan endless abrasive belt while running the belt over an accurately surfaced platen, and maintaining the belt in slidable contactwith the entire surface of the platen by maintaining a film of liquid between the belt and the platen.

. The apparatus herein disclosed consists generally of an enclosed housing in which a pair of pulleysare journalled in spaced apart relationship and over which the abrasive belt is trained. A platen is arranged intermediate the pulleys and preferably adjustable so that it can be-positioned slightly forward of a plane tangent with the Deripheries of the pulleys. Means is arranged within the housing to maintain formed in two sections, a lower or a film of liquid, such as water, or a mixture of water and coolant oil between the back of the belt and the surface of the platen. This means maybe in the nature of one or more nozzles arranged within the housing and effective to maintain amist ing and'adjusted so as to maintain a proper film of the liquid between the belt and platen which I have found causes the belt, probably through surface tension of the liquid,.to slidably cling to the surface of the. platen, and whereby the accuracy of the surface of the platen is reproduced on the article being worked upon.

For convenience in manufacture and assemthe machine is base section ill, I! secured thereto by any not shown. The forbling, the frame or housing of and an upper section suitable means as screws,

, ward side of-the base section l0 extends outtherein, as a motor 26 is pivotally section H), the pulley by means of a belt,

wardly to form a support ing table l3.

As already explained, the abrasive machine is of the belt type, the abrasive belt l4 being trained i2 for a work supportover pulleys l5, l6, journalled in the housing.

I5 is journalled; in the lower base being fixedly secured to a driving shaft. l8 journalled in antifriction bearings I9 carried in a sleeve 20. One side of the base I0 is formed with-an inwardly extending boss 2| apertured to receive the sleeve 20, the outer portion of which is formed with aradial flange 22 apertured to receive screws 23 threading into the base section l0 and thereby securing the sleeve 20, with the drive shaft I8 journalled unit in the frame of the machine. The outer end of the shaft is provided with a driving pulley 24 which is operatively connected with a similar pulley or series of belts, 21.

The driving motor 26 is mounted on the rear side of the base section I0. As here shown, the

mounted, as at 30, to a rearwardly extending bracket 3| provided with screws 33, 34, engaging the base of the motor and providing means for adjusting it about the pivot 30 to effect the proper tension upon the driving belt 21.

The pulley within thehouson a driving motor 26 The upper and lower sections IO, U, of the housing are of substantially box formation, both open at one side, the opening in the lower section In extending to a point below the drive pulley l5, and the opening in the upper section being commensurate therewith; The openings in both sections are closed by a suitable door 31 hinged on the upper section Ii. This arrangement permits convenient assembly of the machine and also the convenient changing of the abrasive belts I4.

The upper pulley I6 is joumalled for free rotation upon a stub shaft 38 pivoted intermediate its ends at 39 to an inwardly extending portion 40 of a slide 4|. The outer end of the stub shaft 38 is pivotally connected, as at 42, to a link 43 vertically adjustable by screw 44 threading into anoutw'ardly extending portion 45 of slide 4|.

The adjacent surface of the upper frame section I I is machined off, and a block 46 is attched thereto as by screws 41. The block 45 is formed with vertically extending dove-tailed ways 4 8and the slide 4| is iormedwith cooperating ways 49. The slide is adjustable vertically relative to the carrying block 46 and the frame of the machine by an adjusting screw 50 having an operating handle 5 l, the adjacent side wall of the upper sec- 7 tion being formed with a concave portion 52 to permit the crank 5| to be operated to permit the slide 4| to be moved upwardly or downwardly by the screw 50 and accordingly, to move the pulley 16 toward and from the bottom pulley l5 to effect proper tension upon the abrasive 'belt l4.

The purpose of the adjustment effected by the screw 44 is to change the angularity between the axis of the pulley 16 with that of -the pulley IS in order to properly track the belt, these adjustments being well understood by those familiar with the belt type abrasive machine.

In addition to being open on. one side, as previously mentioned, the upper section II is also open on the forward side to expose a substantial pipe 13 connected to a feed pipe 14 through a valve 15. The upper nozzle H is connected to a pipe 18 extending downwardly along one side of the upper section II and being connected to the feed pipe 14 through a valve 11, the arrangement being such that nozzles 18, 1| ma be used individually, or in unison. The feed pipe 14 is connected to the outlet port of a circulating pump 18 mounted upon a tank 19 and operable to pump liquid therefrom. The pump 18 is operated by a belt 80 trainedover a pulley 8| carried by the shaft 18.

The lower section I0 is formed with a. transversely extending web 82 of trough formation and one side of the section III is provided with an opening 83 connecting with a tank 84. The tank 84 is provided with an aperture 85 arranged in register with the aperture 83, and the tank 64 is connected to tank 19 by connection 81, all whereby the water or coolant cooled in the base section I0 is permitted to drain into the tank 34 wherein any solid material settles to the bottom of the tank and the liquid passes through connection 81 into tank 18 wherefrom it is pumped to the nozzles 18, II.

The tank 84 i provided with a bafile 88 to assist in the separation of the solid material from the liquid as will be well understood.

The flow of fluid to the nozzles 10, I l, is so adjusted by valves 15, 11, in conjunction with the moving parts of the machine, as to effect a fog or mist within the housing, whereby the back of the belt is moistened to provide a film'of liquid between it and the face of the platen. This result can obviously be accomplished by directing a fine spray' on the back of the belt. However, I have found that by directing the nozzles i0, 1i on the cutting side of the belt, the back of the belt is I properly moistened while an excess of liquid is portion of the belt M, This exposed portion of the belt is backed up by a platen formed with a rearwardly extending web at 6| centrally located, it being formed at each end with elongated apertures 62 to receive screws 63 threaded into bosses 64 extending laterally from one side of the section I I.

With this arrangement, the platen BI is adjustable toward and from the forward run of the belt I4, and also in angular relation to the work supporting table I3. The platen is maintained in adjusted position by screw 65 threaded through boss 66, with the ends of the screws engaging the ends of the web 6| of the platen. The belt engaging surface of the platen 60 is a true flat plane being preferably hand scraped to a surface plate,

' produce this precision surface on. the work being operated upon by a film of liquid maintained between the belt and the face of theplaten by means of one or more nozzles arranged to direct a spray of liquid within the housing of the machine.-

' As here shown, the nozzle I8 is-arranged in" the base section III and positioned to direct a spray on'the face of the abrading belt I 4 adjacent the lower pulley I5. A second nozzle II is positioned in the upper section II and arranged to direct a spray on the face of the belt in proximity to the upper pulley IS. The lower nozzle I. is fed bya applied to the face of the belt which aids materially in the free removal of chips from the abrasive on the belt and thereby permitting the belt to be run at much higher speeds upon a given material.

This method of grinding has the additional advantage of maintaining the belt at a relatively low temperature While, at the same time, permitting it to be operated under considerable tension over the face of the platen. I

With this method, work can be quickly finished to extremely close tolerances without requiring an additional grinding operation on a surface grinder, or other more expensive and slower operating machines.

WhatIclaimis:

1. In a method of precision grinding consisting ing of holding the work against an endless abrasive belt while running the same over a platen having a true fiat surface and holding the back of the work engaging portion of the belt in slidable contact against the surface of the platen by maintaining a film of liquid between the belt and the platen. I l

2. In a. method of precision grinding consisting of holding the work'against an endless abrasive belt while running the belt over a platen having a true flatsurface and holding the belt in slidable contact against the entiresurface of'the platen by maintaining a film of liquid between the belt and the platen.

3. Grinding apparatus comprising a frame, a

pair of pulleys journalled in the frame and spaced apart in parallel relationship, an endless abrasive belt trained over said pulleys, a platen carried by said platen having a flat surface positioned forward of the plane tangent to said pulleys and en-' gaging the rear side of the belt, means operable the housing, said platen having a flat surface en-' gaging the rear side of the belt and being adjust able toward and from the belt, means operable to maintain a film of liquid between said belt and the surface of the platen, and motive means operable to effect rotation of said pulleys.

5. Grinding apparatus comprising an enclosed housing having an opening in one side thereof, a pair of pulleys journalled in the housing in spaced apart parallel relationship, an abrasive belt trained over said pulleys and having a portion exposed through said opening, a work supporting table carried by the housing and positioned exteriorly thereof in juxtaposition to said opening, a platen detachably mounted in the housing and having a flat surface engaging the rear surface of the exposed portion of said belt, said platen being adjustable toward and from the belt and angularly to said table, a, spray nozzle arranged in the housing and being operable to maintain a film of liquid between the belt and the surface of said platen, and motive means operable to effect rotation of said pulleys.

. ARTHUR N. EMMONS. 

